I saw a headline for a review of “Prometheus” that declared: “It’s no Alien.”

While many consider that to be a criticism, I say it’s a good thing. In fact, that is exactly what makes “Prometheus” as good of a film as the original “Alien.” The last thing I wanted was another film in which a brutal alien is killing people in a limited location. We did that on a ship in “Alien,” with marines in a space colony in “Aliens,” on a prison planet in “Alien 3” and on a ship again in “Alien: Resurrection.”

Even the much-maligned “Alien vs. Predator” films followed the same formula, staging the alien attacks in an Antarctic research station and later in small-town America.

The greatest strength – one of many – in “Prometheus” is that it is decidedly not another “Alien” movie. It’s a film that exists entirely in its own framework, only borrowing elements from the series and hinting at things that would happen in other films.

While “Prometheus” is clearly a prequel to the “Alien” franchise, I now understand why Ridley Scott has said multiple times that it’s not a “direct prequel” to the series. It’s not like last year’s “The Thing,” which literally ends to lead into the opening shots of the 1982 classic. “Prometheus” sets the stage for “Alien,” yes, but it leaves plenty unexplained.

So if you’re expecting a retread of Ridley Scott’s original monster movie in space, you’ll be sorely disappointed. And that’s why I think some reviews of the film are coming in so soft.

But what were you really expecting? Even a quick glance over Ridley Scott’s filmography shows that he doesn’t tread the same ground twice. Even films like “Gladiator” and “Kingdom of Heaven,” which share a lot of themes and elements, are entirely different movies. Why would anyone expect “Alien: The Prequel – The Tragic Journey of the Space Jockey”?

At it’s heart, “Prometheus” is a grand piece of speculative fiction, which opens some thought-provoking doors as to humanity, our beginnings, morality and immortality. It’s the story of a scientific vessel traveling to a distant planet to discover our extraterrestrial ancestors. However, upon arrival, the crew finds some terrifying things and uncovers some unpleasant secrets about our origins.

I won’t say anything more than that, but rather will let the film sit for itself. Things in “Prometheus” need to be revealed by the film, not by trailers, marketing and spoilery reviews. Yes, there are bits and pieces you will recognize from the “Alien” universe, but it gives a very different view of that universe.

Noomi Rapace holds her own as the lead of the film, playing a bit of a precursor to Ellen Ripley. Her character is tough, adorable and complex, and she can be both the victim and the hero. She is supported by a strong cast that includes Charlize Theron as the corporate bigwig driving the mission, Guy Pearce as the aging benefactor and Idris Elba as the overly cliched but still enjoyable pilot.

Still, the star that outshines Rapace in this film is Michael Fassbender as David, they synthetic human keeping control of the ship. (Yes, there’s gotta be one of those in every movie, it seems.) Fassbender has been impressive in both indie and mainstream films lately, and here’s another feather in his cap. It’s an understated role, but like any great character, there’s as much in what he doesn’t say and do as is in what he does.

“Prometheus” is best enjoyed is a relative vacuum from the franchise that left Scott’s hands more than 30 years ago. It’s good to be familiar with the films, but it’s best to expect a grand space journey along the lines of “2001: A Space Odyssey” with teeth and less psychedelic drugs. It is not quite what you’ll expect, and it’s a better film for it.